Continuous heating furnace



March 14, 1939. T. STASS|NET 2,150,613

CONTINUOUS HEATING FURNACE i Filed July 26, 1957 of gas.

Several embodiments of the invention are illus- .Patenten Mar. 14, 1939 UNITED lSTATES? 2,150,613 I CONTINUOUS HEATINGFURNACE'- Theodor Stassinet, Dinslaken, Germany Application Julyl 26, 1937, serial No. .155,760 Germany August 11, 1936 9 claims. (cl. 263-6) 'I 'his invention relates to vcontinuous heating furnaces which may be of the pusher type having ametal charging and a metal discharging opening at opposite ends of the furnace.

It .is an object of the invention .to obtain more favorable conditions in the soaking chamber of the furnace. Infurnaces of-the kind described for instance in Patent.1,9 12,933, itis old lto provide a .vertically restricted passage .connecting the abutting ends of the heating andsoaking chambers but this passage byitself. is not able to maintain superatmospheric pressure in the soaking .chamber which is requiredfor satisfactory operation, as will be explained.

With -the lobject of the invention in mind,4

means for imparting whirling motion to the gas flowing through the passage are provided on the transverse wall, or 'on the bottom or on the sidevwalls f the' furnace defining the restricted passage, or on any one'ofsthe. defining members.

Such means may be ribs defined by grooves in any, or all, of the members, or projections from the inner surface of any, or all, of the members.

The whirls increase the resistance to the iiow of gas and by these the required pressure in the soaking chamber is obtained with a lesser volume trated, by way of example moreor less diagrammatically in the accompanying drawing in whichzj- Fig. 1 isa longitudinalfsection of a furnace in which the means for imparting whirling motion to the gas is on 'the transverse wall forming the restricted-passage, Figs. 2, A3, 4 and 5 are longitudinal sections of the passage illustrating variousf modifications of the said means.

Fig. 6 is a section similar to the sectionsin Figs. 2 to 5 but showing a structure for raising means.'

Fig. 7 is-a cross-section of the restricted passage showing a structure forraising and lowering the transverse wall itself.

Fig. 8 is a cross-section showing means for imparting whirling motion arranged in the sole and in lthe side walls of the restricted passage.

Referring now to the drawing, and first to Fig.

1, the furnace I0 has a roof 2 for the pre-heating chamber c and the heating chamber b, a

transverse wall I forming' the restricted passage4 heated, here shown as billets II,-is' introduced suiiicient for .maintaining superatmospheric and lowering .individual components of the causing considerable scaling of the metal.

through-the charging opening I2 and leaves the sOaking'chamber in annealed condition through l the discharging opening I3.

The transverse wall I, Fig. 2, has three trans-l verse grooves I between ribs 3 in its lower sur- 5 I.

lface for the purpose specied.

It is preferred to subdivide the hearth of continuous pusher furnaces into several sections such as c, b, dgand a each of which has its own. object. For instance, a. continuous heating furnace showing this subdivision is described in the patent to. Culbertson, No. 1,912,933. The subdivision of the hearth is indicated by the configuration of the roofs for the several sections, as 2, I, and I4 in Fig. 1. l

Themetal billets. II areheated to the highest temperature in the heating chamber b, It is not enough that the amount of heat required be absorbed by the metal but it is necessary that the temperaturev should be uniform throughout the metal. However, it is very diicult to.l obtain uniform distribution of temperature under the intense Vheating action of the heating chamber b, and therefore the soaking chamber a; is provided and heated by its burner' I5 only to such an extent as to make up for the loss of heat by 'transfer to the side walls, the` roof and the sole of the soaking chamber, and to the gas flowingto thel discharge opening I3, but the metal must not be heated 'to higher temperature in the soaking chamber.

The make-up heat supplied to the soaking chamber is comparatively small and with furnaces having a'. plain transverse Wall I, is not pressure in the soaking chamber, or for filling the soaking chamber vcompletely with furnace gas. The loss through cold air is particularly bad in furnaces in which the` charging opening I2 and the discharging opening I3 are arranged at opposite ends of the-furnace, as shown. Here, the air .is drawn into the soaking chamberza through the discharging opening I3 if the 'pressure in the chamber falls to below atmospheric, 'This must be avoided under al1 conditions.

-Heretofore the only remedy available was to introduce large volumes ,of' furnace or lneutral gas but'this is by no. means satisfactory for-the large volume of such gas, or gases, cause overheating ofthe metal, delay or even prevent uniform vdistribution of temperature in the metal and involve undesirable extra cost. These drawl backs are4 particularly grave during 'shut-down periods. 55

To overcome these drawbacks, it was attempted to reduce to the minimum the clearance between the transverse wall and the plane of travel of the metal but there is a limit to this since the transverse wall must be positioned so as to permit the maximum thickness of metal to pass freely below it, with consideration of the fact that the billets may rise one upon the other and damage the transverse wall if it is arranged at too low a level.

The resistance of restricted passages as provided heretofore was too low under all conditions, even if the transverse wall was lowered to the extent practicable and so it was necessary to supply to the soaking chamber two or three times the volume of combustion and/ or neutral gas required for making up for heat loss.

According to the invention, therefore, the old expedient of whirling is resorted to by providing the means described for imparting whirling motion to the gas as it flows through the restricted passage d. Such means may be arranged in the transverse wall I in the shape` of the transverse grooves 4 hereinabove described, or similar grooves may also be provided in the side walls and/or the sole of the furnace where the restricted passage d is situated.

A transverse wall of this type is simple in design and the resistance it produces is easily calculated. Thel unobstructed cross-section of the passage, or the clearance between the lowest point of the transverse wall I and the furnace sole, is made equal to that provided in the existing furnace.

Whirls or. eddies are produced by the transverse grooves 4 which increase the resistance to -the iiow of gas in the restricted passage d and the same pressure in the soaking chamber a is produced with a smaller volume of furnace and/or neutral gas.

Generally the resistance increases with the number of grooves provided but there should not be too many grooves since it has been found that the resistance decreases if a certain limit number of grooves is overstepped. It has been found, that the efficiency of the restricted passage according to the invention is a maximum if the Reynolds number is 1800 to 5000, and preferably about 2200.

With three grooves 4, as shown in Figs. 1 and 2, the volume of gas required for obtaining the same pressure in the soaking chamber a.' is only onehalf of thatrequired in the existing furnaces, and this volume in many cases is just that required as make-up for heat loss. The heating of the soaking chamber is independent of the furnace operation and the same volume of gas is consumed in the soaking chamber during shut-up periods and periods of increased output, and the metal is not overheated. Heretofore during long shut-down periods the supply of gas to the soaking chamber had to be throttled to prevent overheating but if this is done cold air immediately penetrates into the soaking chamber and causes scaling of the metal. 'Ihis drawback is eliminated according to the invention.

A very simple construction of the transverse wail is obtained by making the bricks 3 which form the ribs deeper than thebricks 4 dening the grooves, as shownifor three grooves 4 in Fig. 2, and for two grooves 4 in Fig. 3.

For increasing the resistance recesses 5 may be formed in the walls of the bricks 3 defining the grooves 4 as shown in Fig. 4, and such recesses may be formed in the rear walls only, as

shown in full lines, or in the front walls also, as shown in dotted lines.

Fig. 5 shows bricks 3' of angular cross-section as defining the grooves 4. The longer shanks of these bricks project below the lower surface of the transverse wall.

the transverse rows may be of equal size, or of different sizes. The resistance is, perhaps, not as high as that of grooves and ribs but on the other hand the transverse wall will stand shocks from the metal .or from furnace implements better than a grooved wall.

'I'he resistance is regulated within certain limits by providing means for raising and lowering the bricks 4 at the bottom of each groove, as shown in Fig. 6. The bricks 4 are suspended from a bracket I1 at the lower end of a steel structure I8, and similar means may be provided for raising and lowering the transversevwall I itself, as shown in Fig. '7. A beam 8, of I.section, is connected to the structure I8 at its top and supported by nuts 9 on a pair of threaded rods 6 secured to the steel plates I9 of the furnace at their lower ends.

Instead of raising and lowering the transverse wall I as a unit, it is possible to suspend any, or all, of the bricks from a structure as described in order to adapt the clearance of the restricted passage d to metal of various thickness, and to attain the minimum gas consumption of the soaking chamber a even with the most difficult shapes of metal parts.

If desired, grooves 2| ymay be made in the side walls 20 of the furnace, at the restricted passage d as shown in Fig. 8, and, if the metal is heated from below in the soaking chamber a, the sole may also be grooved las indicated at 22. Obviously such grooves 2l and/or 22 may be combined with a grooved transverse wall I.

Obviously the invention can be adapted to pusher furnaces in which a welding hearth is provided instead of the soaking chamber a.

In allembodiments of the invention 'superatmospheric pressure is maintained in the soaking chamber a even at its lowest point, with a minimum volume of furnace and/or neutral gas.

l. A continuous heating furnace, comprising, a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall extending downwardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends of the heating and soaking chambers, a bottom, and side walls deining the restricted passage, and ribs on the inner surface of one of the said deningmembers for imparting whirling motion to gas flowing through, the passage, and independent heating means for the heating and soaking chambers.

2. A continuous heating furnace, comprising a heating chamber having a metal charging opening, a soaking chamber having a. metal discharging opening, a transverse wall extending downwardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends oi the heating and soaking chambers, and the face of the transverse wall having grooves for imparting whirling motion to gas flowing through the passage, and independent heating means for the heating and soaking chambers.

3. A continuous heating furnace, comprising a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall having recessed portions extending downwardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends of the heating and soaking chambers to impart a whirling motion tov gases wing through the passage, and independent heating means for said chambers.

4. A continuous heating furnace, comprising a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall having recessed portions arranged transversely of the furnace and to the flow of gas in the furnace and extending downwardly towards the plane of travel of the metal being heated to form a vertically'restricted passage connecting the abutting ends of the heating and soaking chambers to impart a whirling motion to the gases flowing through the passage, and independent heating means for said chambers.

5. A continuous heating furnace, comprising a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall extending downwardly towards the plane of travel of the metal being heated to form a. vertically restricted passage connecting the abutting ends of the heating and soaking chambers, bricks of greater depth alternatingwith bricks of lesser depth on the lower surface of the wall to impart a whirling motion to gases iiowing through the passage, and independent heating means for said chambers.

6. A continuous heating furnace, comprising a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall extending down wardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends of the heating and soaking chambers, and angular bricks projecting from the lower surface of the wall with one of their angle portions extending transverse to the flow of gases between the chambers to impart a whirling motion to the gases owing through the passage, and independent heating means for said chambers.

7. A continuous heating furnace, comprising a heating chamber having a metal. charging opening, a soaking chamber having a metal discharging opening, a transverse wall extending downwardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends of the heating and soaking chambers, bricks of greater depth alternating with bricks of lesser depth on the lower surface of the wall to impart a whirling motion to gases owing through the passage, and independent heating means for said chambers.

8. A continuous heating furnace comprising a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall extending downwardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends of the heating and soaking chambers, bricks of greater depth alternating with bricks of lesser depth on the lower surface of the wall to impart a whirling motion to gases flowing through the passage, means for raising and lowering the bricks which are of lesser depth', and independent heating means for said chambers.y

9. A continuous heating furnace, comprising a heating chamber having a metal charging opening, a soaking chamber having a metal discharging opening, a transverse wall extending downwardly towards the plane of travel of the metal being heated to form a vertically restricted passage connecting the abutting ends of the heating and soaking chambers, means on the lower face of the transverse wall forimparting whirling motion to gas flowing through the passage, means for raising and lowering the transverse wall, and independent heating means for said chambers. THEODOR STASSINET. 

